Ammonia is a widely used chemical with many applications. Example of applications are ammonia as reductant for selective catalytic reduction (SCR) of NOx in exhaust gas from combustion processes or as ammonia-based energy storage for fuel cell applications.
For most applications, and in particular in automotive applications, the storage of ammonia in the form of a pressurized liquid in a vessel is too hazardous. A storage method involving ad- or absorption of molecular ammonia in a solid material kept in a container can circumvent the safety hazard of anhydrous liquid ammonia and enable the use of ammonia in mobile or de-central applications
Metal amine salts are ammonia absorbing and desorbing materials, which can be used as solid storage medium for ammonia (see e.g. WO 2006/012903 A2), which in turn, as mentioned above, may be used as the reductant in selective catalytic reduction to reduce NOx emissions. Using the storage method for ammonia-mediated energy storage for fuel cell applications is another attractive field of application.
The initial saturation of ammonia storage material in a container with ammonia is, of course, accomplished before the container, after saturation of the storage material which may be accomplished within the container, is mounted on a vehicle or attached to another system where it is used. On-board re-saturation of storage material which is ammonia-depleted by consumption is impractical because of the requirement of liquid ammonia storage by the end user. Therefore, the container should rather be replaced by a unit that is fully saturated and the partly or fully ammonia-depleted unit should be re-saturated in a facility suited for this. However, industrial facilities for the cost-effective re-saturation of ammonia storage material in containers with reliable quality assurance methods required for automotive applications do not exist on the market and a simple process with low degree of individual monitoring for providing a reliable product is required.